This invention relates to an improved tool for adjusting carburetors of internal combustion engines, and more particularly a tool for quickly and accurately adjusting the idle mixture controls on the carburetors of multiple or single barrelled automobile carburetors. A large percentage of gasoline automobile engines are equipped with double barrelled carburetors. For example, a V-8 engine invariably has two intake manifolds, one connected to each of the two sides thereof, with each of the two barrels of a double barrelled carburetor connected to a different one of the intake manifolds, or each pair of barrels of a four barrelled carburetor to a different one of the intake manifolds. Most modern carburetors have fixed metering rods for vaporizing the gasoline at speeds above idle and have adjustable idle mixture screws for controlling the air to fuel mixture ratio at low or idling speeds. The proper adjustment of these controls insures that the engine will idle at a speed which will prevent engine stalling and also will not result in excessive air pollution which can result from an overly rich mixture. Lean mixtures can result in stalling and also causes engine overheating if the engine idles for long periods. Multiple barrelled carburetors are in effect two or more separate carburetors in a common housing and the idle mixture adjustments must both or all be separately adjusted for optimum operation. The usual practice prior to the present invention was to close the idle mixture needle valves by turning the idle mixture adjustment screws all the way in. The valves would then be gradually opened by alternately unscrewing each adjustment screw while listening to the engine, checking the exhaust or obtaining a desired idle rpm. A simple screwdriver was usually used for this adjustment.
The present invention provides a tool which can simultaneously adjust both of the idle mixture adjustment screws of a double barrelled carburetor, and it is also capable of independently adjusting either one of these screws, to fine tune the adjustment so that both carburetor barrels will be adjusted in an optimum manner. The tool can also be used to adjust single barrelled and four barrelled carburetors.